A metabolic disease is a syndrome that appears with the risk factors such as obesity, diabetes, hypertension and arteriosclerosis caused by excessive nutrition accumulation in the body and lack of exercise. In recent years, it has been formally named the metabolic syndrome or insulin resistance syndrome through the Adult Treatment Program Panel III established by the World Health Organization and the National Heart, Lung, and Blood Institute of the National Institutes of Health. In addition, according to the ATP of the USA National Cholesterol Education Program (NCEP) announced in 2001, it is judged to be a metabolic disease if a patient showing at least three of the five risk factors of abdominal obesity with a waist circumference of 40 inches (102 cm) or longer for men and 35 inches (88 cm) or longer for women, triglycerides of 150 mg/DL or higher, HDL cholesterol of 40 mg/dL or less for men and 50 mg/dL or less for women, blood pressure of 130/85 mmHg or higher, and fasting glucose of 110 mg/dL or higher. In case of Asians, it has been somewhat adjusted that the waist circumference of 90 cm or longer for men and 80 cm or longer for women is considered as abdominal obesity. When these rules are applied, there is a recent study showing that approximately 25% of Koreans among the entire population shows metabolic syndrome symptoms.
On the other hand, mucosal immune tissues refer to tissues covered with mucous membranes ranging from respiratory organs, genital organs and digestive organs, and these tissues are directly connected to the external environment and are easily exposed to foreign antigens and pathogens. In the mucosal tissues of a human body, various microorganisms of nearly 100 trillion such as bacteria, fungi, protozoa, etc. produce clustering, and coexist with them.
In comparison of systemic immune tissues, mucosal immune tissues have an immunological tolerance mechanism to coexist with various symbiotic microorganisms, and at the same time, it has a system that can cause rapid and powerful immune response for the primary defense against pathogenic microorganisms.
Intestinal microorganisms are known to affect human health and diseases by participating in the maintenance of intestinal homeostasis and metabolic regulation through many mechanisms. Intestinal microorganisms ferment undigested polysaccharides to prepare short chain fatty acids and supply the energy source of intestinal epithelial cells. Intestinal microflora of a human being may be broadly divided into four phyla of gram-negative bacteria, Bacteroidetes and Proteobacteira, and gram-positive bacteria, Firmicutes and Actinobacteria.
In particular, obesity is one of the health risk factors associated with diseases such as cardiovascular disease, diabetes and osteoporosis. Recently, many research results have been published showing that obesity is deeply related to changes and diversity of intestinal microflora. In comparison of the intestinal microorganisms of an obese mouse (ob/ob mouse) with those of a normal body weight mouse, it is known that Firmicutes phylum is increased and Bacteroides phylum is decreased. Similarly, it has been reported that when low-carbohydrate or low-fat meals are served to obese humans, Bacteroidetes phylum is increased, and in a study of twins, the diversity is decreased and Bacteroidetes phylum is decreased on analysis of intestinal microorganisms of obese humans.
As a result of analyzing intestinal microorganism genetic makeups in lean and obese humans, it was confirmed that there are significant differences in the type and amount of intestinal microbial species. In other words, the result has been reported that obese patients who do not have abundant intestinal microorganisms show symptoms such as adiposity, insulin resistance, dyslipidemia, and inflammatory reaction, and gain body weight more easily than obese humans with abundant intestinal microorganisms.
The interaction between intestinal microorganisms and hosts play an important role in the pathogenesis of obesity and metabolic syndrome. There is a high possibility of preventing/treating obesity by investigating and isolating/identifying the role of microorganisms that are symbiotic in the intestine and causing changes in these interactions using the concept of probiotics.
However, it has not yet been proven that certain intestinal microorganisms are directly involved in lipid metabolism and can affect body weight and fat mass.